This invention relates to a vertical drilling rig having a drive kelly for a drilling tool supported therefrom and more particularly to such a drilling rig which includes a hydraulically driven crowd for the drive kelly.
In vertical drill rigs it has long been the established practice to utilize a drive kelly having a drilling tool supported from its lower end, and at some point along its vertical length the drive kelly passes through an opening in a rotary table having a roller drive unit supported thereon. The rotary table is drivingly rotated for imparting a rotating movement through the roller drive unit to the drive kelly and thus the drilling tool. If the hole being drilled is very shallow, or the formation is very soft, the downward vertical drive of the drilling tool can be accomplished by gravity alone. That is, the combined weight of the drilling tool and the drive kelly are sufficient to drive the drilling tool downward at the necessary penetration rate of travel.
In many instances, however, when the depth of the hole becomes greater or the formation of the ground being cut is relatively hard, then the mere weight of the equipment is no longer sufficient to accomplish the drilling action at a satisfactory penetration rate. It then becomes necessary, or at least advantageous, to accelerate the downward travel of the drilling tool by "crowding" the kelly.
It has heretofore been known to utilize a crowd mechanism having a positive drive such that a powered downward movement of the crowd mechanism is fully and directly imparted to the drive kelly and hence to the drilling tool. Another known type of crowd mechanism is the friction crowd in which another member is placed in longitudinal sliding engagement with the drive kelly and is moved downwardly in order to at least partially transmit its downward movement through the drive kelly to the drilling tool. A drive kelly utilizing a type of friction crowd has been disclosed in U.S. Pat. No. 3,987,856.
In drilling relatively deep holes such as 100 feet or more, it is generally the practice to utilize either a double kelly or a triple kelly. Thus the kelly is provided with multiple members which have a longitudinal telescopically collapsed position in which they are concentrically arranged, or which any be longitudinally extended so that each member overlaps a small portion of the length of the next.
It will be evident that the arrangement of the vertical drilling rig, including its rotary table, drive kelly and crowd mechanism, generates a rather complex problem when an effort is made to achieve maximum drilling speeds, maximum depth of hole to be cut, and at the same time maintaining the original cost of equipment as well as the maintenance expense thereof at minimum levels.
It is therefore the purpose and object of the present invention to provide a crowd mechanism for a drive kelly of a vertical drilling rig which has advantages not obtainable with previously known types of crowd mechanims.
Another object of the present invention is to provide a hydraulically driven kelly crowd mechanism for a vertical drilling rig which provides for the crowd load applied on the drive kelly to remain substantially constant while enabling the vertical penetration rate of the rotating drilling tool supported from the lower end of the drive kelly to automatically vary in accordance with the hardness of the formation of the earth encountered during the drilling of a hole.
Another object of the present invention is to provide from crowding a drill kelly having a drilling tool on the lower end thereof by providing apparatus for automatically and simultaneously lowering and pulling down the swivel head of the drive kelly at a rate which varies in accordance with the variation of the hardness of the formation of the earth being drilled by the drilling tool.
With these and other objects in view, the invention consists in the construction, arrangement, and combination of the various parts of the device whereby the objects contemplated are attained as hereinafter set forth, pointed out in the appended claims and illustrated in the accompanying drawings.